1. Field of the Invention
This invention is directed to coatings for implantable medical devices, such as drug eluting vascular stents.
2. Description of the State of the Art
Percutaneous transluminal coronary angioplasty (PTCA) is a procedure for treating heart disease. A catheter assembly having a balloon portion is introduced percutaneously into the cardiovascular system of a patient via the brachial or femoral artery. The catheter assembly is advanced through the coronary vasculature until the balloon portion is positioned across the occlusive lesion. Once in position across the lesion, the balloon is inflated to a predetermined size to radially compress against the atherosclerotic plaque of the lesion to remodel the lumen wall. The balloon is then deflated to a smaller profile to allow the catheter to be withdrawn from the patient's vasculature. polymer dissolved in the solvent, and a therapeutic substance dispersed in the blend is applied to the stent. The solvent is allowed to evaporate, leaving on the stent surface a coating of the polymer and the therapeutic substance impregnated in the polymer. Once the stent has been implanted at the treatment site, the therapeutic substance has a sustained release profile from the polymer.
Although local administration of therapeutic agents via stents has shown favorable results in reducing restenosis, improvements can be made to the coatings, more particularly improvements of the biological compatibility of the coatings. The embodiments of the present invention provide for biologically compatible polymers and combination of polymers for coating stents and other implantable medical devices.